Ureteral stent

ABSTRACT

A stent is designed to be placed within a patient&#39;s ureter to facilitate drainage from the patient&#39;s kidneys to the bladder. An elongated portion of the stent includes a length sufficient to extend substantially within the ureter from the kidney to the bladder, and defines a lumen extending therethrough. A first end portion extends from one end of the elongated portion and is adapted to assume a retaining configuration when placed substantially within the kidney. A second end portion extends from another end of the elongated portion and flares outward when placed substantially within the bladder to maintain position. The second end portion allows fluids to flow through the lumen and into the bladder and is collapsible to prevent fluid from passing from the bladder to the kidney.

TECHNICAL FIELD

This invention relates to stents and methods of maintaining patency of abody lumen such as the ureter using stents.

BACKGROUND INFORMATION

A ureter is a tubular passageway in a body that conveys urine from thekidney to the bladder. Urine is transported through the ureter under theinfluence of hydrostatic pressure assisted by contractions of muscleslocated within the walls (lining) of the ureter. A urological conditionthat some patients experience is ureteral blockage or obstruction. Somecommon causes of such blockage are the formation of tumors orabnormalities within the ureteral lining or the formation and passage ofkidney stones.

Ureteral stents are medical devices designed to extend through theureter and to facilitate drainage from a kidney to the bladder when theureter becomes blocked or obstructed. Generally, these stents are madefrom small diameter tubing of a biocompatible plastic. Ureteral stentsmay have multiple side holes to enhance drainage and typically includeretention hooks or coils extending from both the kidney (distal) andbladder (proximal) ends of the tubing to prevent the migration of theureteral stent after placement within the ureter.

SUMMARY OF THE INVENTION

The present invention generally relates to draining fluids from thekidney to the bladder of a patient with a stent. Devices and methodsaccording to the invention are typically used in the treatment ofpatients suffering from an obstructed ureter to address and relieveurinary retention while minimizing patient discomfort. It is an objectof the invention to maintain the ureter open and able to pass fluidsfrom the kidney to the bladder. It is another object of the invention tominimize patient discomfort associated with a placed ureteral stent.

In one aspect, the invention relates to a ureteral stent. The ureteralstent includes an elongated portion, a first end portion extending fromone end of the elongated portion, and a second end portion extendingfrom another end of the elongated portion. The elongated portion has alength sufficient to extend substantially within the ureter from thekidney to the bladder and defines a lumen extending within. The firstend portion is adapted to assume a retaining configuration when placedsubstantially within the kidney. The first end portion includes aninterior space in communication with the lumen of the elongated portionand at least one opening in communication with the interior space forurine drainage from the kidney to the ureteral stent. The second endportion flares outward when placed substantially within the bladder tomaintain position substantially within the bladder. The second endportion is collapsible to prevent fluid from passing into the lumen andcausing patient discomfort.

Embodiments of this aspect of the invention can include the followingfeatures. In one embodiment, the second end portion includes a pleatedsegment including a plurality of folds at a wider part of the second endportion. The plurality of folds increase the bulk of the second endportion and facilitate retention of the second end portion substantiallywithin the bladder. The pleated segment may be formed from a polymer,such as silicone or ethylene-vinyl acetate, or a polymer solution, suchas a mixture of polyurethane and polycarbonate.

In another embodiment, the second end portion includes a plurality ofinner segments and a plurality of outer segments. The second end portionis configured such that each one of the plurality of outer segmentsoverlaps at least one of the plurality of inner segments. The pluralityof inner and outer segments may be formed from a polymer or a polymersolution of polyurethane and polycarbonate. Additionally, the pluralityof inner and outer segments may include a plurality of folds to increasethe bulk of the second end portion, thereby facilitating retention ofthe second end portion within the bladder and facilitating prevention ofurine from the bladder from entering the second end portion.

In yet another embodiment, the second end portion includes a pluralityof segments, wherein each one of the plurality of segments is adjacentand overlapping at least one other segment of the plurality of segments.The plurality of segments may be formed from a polymer or a polymersolution, such as a polymer solution of polyurethane and polycarbonate.In some embodiments, the plurality of segments may include a pluralityof folds to increase the bulk of the second end portion.

In another aspect, the invention relates to a ureteral stent. Theureteral stent, according to this aspect of the invention, includes anelongated portion, a first end portion extending from one end of theelongated portion, and a second end portion extending from another endof the elongated portion. The elongated portion has a length sufficientto extend substantially within the ureter from the kidney to the bladderand defines a lumen extending within. The first end portion is adaptedto assume a retaining configuration when placed substantially within thekidney. The first end portion includes an interior space incommunication with the lumen of the elongated portion and at least oneopening in communication with the interior space for urine drainage fromthe kidney to the ureteral stent. The second end portion is wrapped toform a conical structure. The second end portion is adapted forplacement and for maintaining position substantially within the bladder.

Embodiments of this aspect of the invention can include the followingfeatures. In one embodiment, the conical structure includes a first end,a second end including a width greater than a width of the first end,and a coiled segment disposed between the first and second ends. Thecoiled segment includes at least one and a half windings. In anotherembodiment, the second end portion is made from a biocompatiblematerial, such as, for example, a polymer, a polymer solution ofpolyurethane and polycarbonate, or from a super-elastic material, suchas, a nickel-titanium alloy. In some embodiments, the second end portionincludes a mesh to allow for drainage of urine from the second endportion. In another embodiment, the second end portion includes one ormore tails for transporting liquid, such as, urine, to the bladder whenthe stent is placed within a patient.

In general, in another aspect, the invention features a method ofinserting within a urinary system a ureteral stent, such as, one of thestents described above. The method includes inserting the stent into theurinary system of a patient and positioning the ureteral stent withinthe ureter such that the first end portion is within the kidney and thesecond end portion is within the bladder. The method may further includeproviding a catheter sized to receive the ureteral stent and using thecatheter to insert and position the ureteral stent within the urinarysystem.

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent from the following descriptionand from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention.

FIG. 1 is a schematic view of one embodiment of a stent according to theinvention within a human urinary system.

FIG. 2A is a side view of the stent of FIG. 1.

FIG. 2B is an enlarged side view of a proximal portion of the stent ofFIG. 2A.

FIG. 2C is a cross-sectional view of the proximal portion of the stentof FIG. 2B in an open configuration, taken along line AA of FIG. 2B.

FIG. 2D is a bottom view of the proximal portion of the stent of FIG. 2Bin the open configuration.

FIG. 2E is a bottom view of the proximal portion of the stent of FIG. 2Bin a collapsed configuration.

FIG. 2F is a schematic view of the proximal portion of the stent in theopen configuration, allowing fluid to pass therethrough.

FIG. 2G is a schematic view of the proximal portion of the stent in thecollapsed configuration, preventing fluid to flow into the proximalportion of the stent.

FIG. 2H is an enlarged prospective view of one embodiment of a segmentof the proximal portion of a stent according to the invention.

FIG. 3A is an enlarged side view of a proximal portion of anotherembodiment of a stent according to the invention.

FIG. 3B is a cross-sectional view of the proximal portion of the stentof FIG. 3A in an open configuration, taken along line BB in FIG. 3A.

FIG. 3C is a bottom view of the proximal portion of the stent of FIG. 3Ain an open configuration.

FIG. 3D is a bottom view of the proximal portion of the stent of FIG. 3Ain a collapsed configuration.

FIG. 4A is an enlarged side view of a proximal portion of anotherembodiment of a stent according to the invention.

FIG. 4B is a cross-sectional view of the proximal portion of the stentof FIG. 4A in an open configuration, taken along line CC in FIG. 4A.

FIG. 4C is a cross-sectional view of the proximal portion of the stentof FIG. 4A in a collapsed configuration, taken along line CC in FIG. 4A.

FIG. 5A is an enlarged side view of a proximal portion of anotherembodiment of a stent according to the invention in an openconfiguration.

FIG. 5B is another enlarged side view of the proximal portion of thestent of FIG. 5A in a collapsed configuration.

FIG. 6A is an enlarged side view of a proximal portion of anotherembodiment of a stent according to the invention.

FIG. 6B is a cross-sectional view of the proximal portion of the stentof FIG. 6A in an open configuration, taken along line DD in FIG. 6A.

FIG. 6C is a cross-sectional view of the proximal portion of the stentof FIG. 6A in a collapsed configuration, taken along line DD in FIG. 6A.

FIG. 7A is an enlarged perspective view of a proximal portion of anotherembodiment of a stent according to the invention in an insertedconfiguration.

FIG. 7B is another enlarged perspective view of the proximal portion ofthe stent of FIG. 7A in an expanded configuration.

FIG. 7C is an enlarged perspective view of a proximal portion of anotherembodiment of a stent according to the invention.

FIG. 7D is an enlarged perspective view of a proximal portion of anotherembodiment of a stent according to the invention.

DESCRIPTION

Referring to FIG. 1, in a human urinary system 100, the ureters 110transport urine from the kidneys 105 to the bladder 120. When one orboth of the ureters 110 become blocked or obstructed due to, forexample, the growth of a tumor or the entrapment of a kidney stone, atemporary alternative path is needed to provide fluid drainage between apatient's kidneys 105 and bladder 120. Ureteral stents are medicaldevices that are positioned within the ureters 110 to restore theirpatency and fluid drainage. Conventional ureteral stents have coiled orhooked ends adapted to retain the stent within the ureter 110. In thebladder 120, these end structures contact the bladder lining within aregion of the bladder 120 known as the trigone 130.

The trigone 130 is located between the patient's uretheral opening 135and two ureteral orifices 115. The trigone 130 contains a nerve bed andthus is a sensitive region of the bladder 120. Foreign objects, such asconventional stent end structures, placed within the trigone 130stimulate the nerve bed causing the patient to experience bladder painand irritation. The patient's discomfort arising from use of aconvention ureteral stent may be increased if urine collects within theend structure in the bladder 120 and then is hydrostatically forced, dueto pressure build up, to flow in a retrograde motion from the bladder120 to the kidney 105.

The present invention concerns ureteral stents that reduce patientirritation and discomfort when placed within the ureter. The ureteralstents of the present invention include a bladder end structure that ispositioned substantially within the bladder and is adapted to allowfluid, such as, urine, to flow through a lumen within the stent and intoa patient's bladder. The bladder end structure flares outward whenpositioned in the bladder to prevent migration. To increase patientcomfort, the stent's bladder end structure is collapsible in the absenceof fluid flowing through the lumen to the bladder, thereby preventingretrograde motion of fluid from the bladder to the kidney. The bladderend structure may be made from a biocompatible material, such as, forexample, a polymer (such as silicone, polyethylene terephthalate,tetrafluoroethylene, or ethylene-vinyl acetate) or a polymer solution(such as a mixture of polyurethane and polycarbonate).

Referring to FIGS. 1 and 2A, a stent 200 according to the inventionincludes an elongated portion 205 that spans between a first and asecond end portions 220, 230. The elongated portion 205 has a sufficientlength to extend substantially the entire ureter 110 from the kidney 105to the bladder 120. Within the elongated portion 205 is a lumen fortransporting urine or other bodily fluids from the kidney 105 to thebladder 120. Located along the length of the elongated portion 205 canbe a plurality of openings 207 in communication with the lumen. Theseopenings are optional, and if present tend to increase drainage of urinethrough the stent 200 and into the bladder 120.

The first and second end portions 220, 230 extend from opposite ends ofthe elongated portion 205 and have shapes adapted to retain the ureteralstent 200 within the ureter. In the embodiment shown in FIG. 2A, thefirst end portion 220 extends from a distal end 215 of the elongatedportion 205 and has a pigtail coil shape that can be temporarilystraightened for insertion and recoiled once positioned within thekidney 105. Alternatively, in some embodiments, the first end portion220 may have a hook shaped end to anchor and inhibit downward movementof the ureteral stent 200 from the kidney 105 towards the bladder 120.In either embodiment, within the first end portion 220 lies a lumen,which is in fluid communication with the lumen extending through theelongated portion 205. To allow fluid from the kidney to enter into theureteral stent 200, the first end portion 220 has at least one opening210 in communication with the lumen.

The second end portion 230 extends from a proximal end 225 of theelongated portion 205. The second end portion 230 anchors and preventsthe upward motion of the ureteral stent 200. The second end portion 230is a bulky, lightweight structure that has a large volume to weightratio. The second end portion 230, as shown in FIGS. 2A-2D, has aplurality of segments 235, including a plurality of inner segments 236and a plurality of outer segments 237. Each one of the plurality ofouter segments 237 overlaps at least one of the plurality of innersegments 236 to form radially overlapping portions 240. FIG. 2C showsthe radially overlapping portions 240 in this embodiment. A radial wedgelabeled β 233 in FIG. 2C outlines a portion of the radial overlappingportions 240 of a representative inner segments 236 and in an adjacentouter segments 237. The inner and outer segment 236, 237 are made from amaterial that is soft and flexible, such as a biocompatible polymer orpolymer solution. Examples of suitable polymers or polymer solutions aresilicone, polyethylene terephthalate, tetrafluoroethylene,ethylene-vinyl acetate, and a mixture of polycarbonate and polyurethane.The segments 235 may be attached to the proximal end 225 of theelongated portion 205 by thermal bonding or adhesive.

The segments 235 overlap creating a volume mass that will inhibit theureteral stent 200 from migrating from the bladder 120. The overlappingportions 240 also inhibit fluid, such as urine, from returning into theelongated portion 205 once the fluid enters the bladder 120 by limitingfluid access to the lumen in the elongated portion 205. In theembodiment shown in FIGS. 2D-2E, the segments 235 are arranged in aconcentric pattern extending outwards from the proximal end 225. Theplurality of segments 235 are adapted to collapse in on themselves inthe absence of fluid flowing from the elongated portion 205 through thesecond end portion 230. Referring to FIG. 2F, the segments 235, becauseof their flexibility and minimal weight, are pushed radially outward bythe force of the flowing fluid 245 through the second end portion 230,thereby allowing the fluid to easily escape from the ureteral stent 200.Once the fluid has ceased flowing through the stent 200, the segments235 collapse in on each other inhibiting fluid 245 from re-entering theureteral stent 200, as shown in FIG. 2G.

Each of the segments 235 may be folded or waved, such that the segments235 resemble seaweed, to increase the bulk of the second end portion 230of the stent 200. FIG. 2H is a perspective view of a waved segment 235.Individual folds 246 not only increase the bulk of the second endportion 230, but also inhibit urine from entering into the lumen of thestent 200 when the second end portion 230 is collapsed. The folds 246 ofthe segments 235 overlap when the second end portion 230 is collapsed tocover an opening to the lumen proximate to the proximal end 225 of theelongated portion 205.

In another embodiment, the second end portion includes a plurality ofsegments 235. Each one of the plurality of segments 235 is adjacent andoverlapping at least one other segment. The plurality of segments 235are configured to provide bulk to the second end portion 230, such thatthe second end portion 230 is anchored within the bladder 120, therebypreventing distal migration of the stent 200. The plurality of segments235 overlap to form radially overlapping portions 240 as outlined byradial wedges labeled β 233 in FIG. 3B.

Referring to FIGS. 3C-3D, the second end portion 230 has at least twodifferent configurations. While the stent is actively draining fluidstherethrough, the second end portion 230 is in an open configuration asshown in FIG. 3C. FIG. 3C shows a bottom view of the second end portion230 of the stent 200 in the open configuration. As described above,fluid flowing under the influence of gravity forces the plurality ofsegments 235 to separate to allow passage of fluid therethrough. In theabsence of flowing fluid, the plurality of segments 235 collapse in onthemselves, as shown in FIG. 3D, thereby preventing fluid from enteringthe lumen of the stent at the proximal end 225.

In another embodiment shown in FIGS. 4A-4C, the second end portion 230includes a single segment 235 made from a polymer such as silicone,polyethylene terephthalate, tetrafluoroethylene, or ethylene-vinylacetate, or from a polymer solution of polycarbonate and polyurethane.The segment 235 folds over upon itself to form the radially overlappingportions 240. The radial wedges β 233 in FIGS. 4B-4C outline some of theradially overlapping portions 240 created by folds 239 in the segment235. In FIGS. 4B and 4C, the folds 239 create a substantially regularpattern around the perimeter of the second end portion 230. FIGS. 4B and4C show cross-sectional views of the second end portion 230 with asingle segment 235 having a substantially regular folding pattern aroundits perimeter. FIG. 4B represents the second end portion 230 in an openfluid flow configuration and FIG. 4C represents the second end portion235 in a closed configuration. Alternatively, the folds 239 in thesecond end portion 230 may form an irregular or non-distinct patternaround its perimeter, as shown in FIGS. 5A and 5B. FIG. 5A representsthe second end portion 230 having a single segment 235 with an irregularfolding pattern in the open configuration. FIG. 5B is an illustration ofthe second end portion 230 of FIG. 5A in the closed configuration. Thefolds 239 within the segment 235, through their volume, impede distalmigration of the stent 200 from its position within the ureter. Thefolds 239 in the segment 235, when the second end portion 230 iscollapsed, also prevent fluid from the bladder from entering the lumenof the elongated portion 205.

In yet another embodiment shown in FIGS. 6A-6C, the second end portion230 includes a segment 235 with pleats 247 at a wider part of the secondend portion 230 to allow the segment 235 to temporarily expand, as shownin FIG. 6B, to drain the ureteral stent 200 during urination. Thesegment 235 is made from a polymer or a polymer solution and is soft andflexible such that the presence of the segment 235 within the bladderdoes not stimulate the trigone. The second end portion 230 will returnto its original configuration as shown in FIG. 4C in the absence offluid flow, and thereby limit fluid access from re-entering the lumen ofthe elongated portion 205. The pleats 247 in the segment 235 provide thesecond end portion 230 with a bulky configuration, which will preventthe second end portion 230 from migrating from its placed positionwithin the bladder. The pleats 247 fold to create radially overlappingportions 240, a portion of which is outline by radial wedges β 233. Theradially overlapping portions 240 add bulk to the second end portion230, which facilitates distal migration prevention.

Referring to FIGS. 7A-7B, in another embodiment, the second end portion230 is formed from a single segment 235 that is wrapped around itself,to form a conical structure 250 for maintaining position of the secondend portion 230 substantially within the bladder 120. Embedded withinthe segment 235 may be a thin wire 255 of super-elastic material, suchas a nickel-titanium alloy, that expands upon a phase change, therebyplacing the second end portion 230 in an open configuration as shown inFIG. 7B. In a closed configuration, as shown in FIG. 7A, the second endportion 230 may be easily inserted and positioned within the body of apatient. The second end portion 230, shown in FIGS. 7A-7B, may bemanufactured using the following procedure. First, the thin wire 255 ispreformed to have a coil shape. Next, the thin wire 255 is temporarilystraightened to be embedded within the segment 235. Preferably, thesegment 235 is a thin (about 0.002 millimeters to 3 millimeters thick)rectangular, polymer sheet. Then, the thin wire 255 is placed along adiagonal of the segment 235 so that a corner of the rectangular sheetmay be folded over the thin wire 255 enclosing the thin wire 255 withinthe segment 235. Next, the polymer segment 235 is heated to encase thethin wire 255 within the segment. Finally, the thin wire 255 is allowedto re-coil, thereby creating the conical structure 250 shown in FIGS.7A-7B, which is then thermally bonded to the elongated portion 205 toproduced the stent 200.

The conical structure 250 shown in FIGS. 7A-7B has a first end 251, asecond end 252, and a coiled segment 253 disposed between the first andsecond ends 251, 252. The second end 252 has a width greater than thewidth of the first end 251 and by its width prevents distal migration ofthe second end portion 230 from the bladder 120 into the ureter 110. Thecoiled segment 253 includes at least one and a half windings forming theconical structure 250.

Referring to FIG. 7C, in some embodiments to prevent a build up of urinewithin the second end portion 230, the segment 235 may include a mesh260. The mesh 260 includes a plurality of openings 262 for the urine orother fluid to pass through, thereby preventing collection or build upof urine within the second end portion 230. In other embodiments, theureteral stent 200 may further include one or more tails 265 extendingfrom an inner surface 270 of the second end portion 230. The tails 265,as shown in FIG. 7D, transport liquid by capillary action through thesecond end portion 230 to the bladder 120. The tails 265 may be attachednear the proximal end 225 of the elongated portion 205 or,alternatively, the tails 265 may be attached near the first end portion220 and extend through the entire ureteral stent 200. The tails 265provide a surface to transport fluid through the second end portion 230.In the embodiment shown in FIG. 7D, the tails 265 allow the second endportion 230 to remain in a substantially closed configuration duringurination, thereby limiting urine from re-entering the lumen of theelongated portion 205 and preventing patient discomfort.

In operation, the ureteral stent 200 is inserted through a patient'surethra and advanced through the bladder 120 and ureter 110 to thekidney 105. Prior to insertion, the first end portion 220 is temporarilystraightened and the second end portion 230 may be temporarilycompressed for insertion into the patient's body.

The first end portion 220 may be straightened over a guide wire, whichslides within the lumen of the ureteral stent 200 and is sufficientlystiff to hold the first end portion 220 in a straight configuration wheninserting the ureteral stent 200. Alternatively, if other end structuresother than a coil are used, such as hooks or malecots, these endstructures are placed in an insertion configuration by for example,straightening the hooks or collapsing the malecots. Prior to insertioninto the urinary system 100, the stent 200 may be disposed within acatheter or a cystoscope. The catheter or cystoscope compresses thesecond end portion 230 to facilitate insertion.

To position the ureteral stent 200 within the urinary system 100 of apatient, a medical professional, such as a physician inserts theguidewire into the patient's urethra and advances the guidewire until adistal end of the guidewire is located within one of the kidneys 105.After properly positioning the guidewire, the physician slides thecatheter or cystoscope over the guidewire and then slides the ureteralstent 200 up over the guidewire, but within the lumen of the cystoscope.The physician may use a pusher to advance the ureteral stent 200 throughthe urinary system until the first end portion 220 is located within thekidney 105 and the second end portion 230 is within the bladder 120.Once positioned, the physician removes the catheter and guidewire fromthe patient's body, thereby allowing the first end portion 220 tore-coil and anchor itself within the kidney 105 and the second endportion 230 to maintain position within the bladder 120.

Variations, modifications, and other implementations of what isdescribed herein will occur to those of ordinary skill in the artwithout departing from the spirit and scope of the invention. Theinvention is not to be limited only to the preceding illustrativedescription.

1. A ureteral stent, comprising: (a) an elongated portion defining alumen extending therethrough and including a length sufficient to extendsubstantially within the ureter from the kidney to the bladder; (b) afirst end portion extending from one end of the elongated portion,defining an interior space in communication with the lumen, and definingat least one opening in communication with the interior space, the firstend portion for placement substantially within the kidney and adapted toassume a retaining configuration when placed substantially within thekidney; and (c) a second end portion extending from another end of theelongated portion and flaring outward when placed substantially withinthe bladder to maintain position substantially within the bladder, thesecond end portion being self-collapsible after implantation to at leastpartially prevent fluid from passing into the lumen.
 2. The stent ofclaim 1 wherein the second end portion comprises a pleated segmentincluding a plurality of folds at a wider part of the second endportion.
 3. The stent of claim 2 wherein the pleated segment comprises apolymer.
 4. The stent of claim 2 wherein the pleated segment comprises apolymer solution.
 5. The stent of claim 4 wherein the polymer solutioncomprises polyurethane and polycarbonate.
 6. The stent of claim 1wherein the second end portion comprises a plurality of inner segmentsand a plurality of outer segments, each one of the plurality of outersegments overlapping at least one of the plurality of inner segments. 7.The stent of claim 6 wherein the plurality of inner and outer segmentscomprise a polymer.
 8. The stent of claim 6 wherein the plurality ofinner and outer segments comprise a polymer solution.
 9. The stent ofclaim 8 wherein the polymer solution comprises polyurethane andpolycarbonate.
 10. The stent according to claim 6 wherein each one ofthe plurality of inner and outer segments includes a plurality of folds.11. The stent of claim 1 wherein the second end portion comprises aplurality of segments, each one of the plurality of segments beingadjacent and overlapping at least one other of the plurality ofsegments.
 12. The stent of claim 11 wherein the plurality of segmentscomprise a polymer.
 13. The stent of claim 11 wherein the plurality ofsegments comprise a polymer solution.
 14. The stent of claim 13 whereinthe polymer solution comprises polyurethane and polycarbonate.
 15. Thestent according to claim 11 wherein each one of the plurality ofsegments includes a plurality of folds.
 16. A method of placing aureteral stent into a urinary system, comprising: (a) providing aureteral stent comprising (i) an elongated portion defining a lumenextending therethrough and including a length sufficient to extendsubstantially within the ureter from the kidney to the bladder, (ii) afirst end portion extending from one end of the elongated portion,defining an interior space in communication with the lumen, and definingat least one opening in communication with the interior space, the firstend portion for placement substantially within the kidney and adapted toassume a retaining configuration when placed substantially within thekidney, and (iii) a second end portion extending from another end of theelongated portion and flaring outward when placed substantially withinthe bladder to maintain position substantially within the bladder, thesecond end portion being self-collapsible after implantation to at leastpartially prevent fluid from passing into the lumen; (b) inserting theureteral stent into the urinary system; and (c) positioning the ureteralstent within the ureter such that the first end portion of the ureteralstent is substantially within the kidney and the second end portion issubstantially within the bladder.
 17. The method of claim 16 furthercomprising: (d) providing a catheter; (e) inserting the ureteral stentwithin the catheter prior to inserting the ureteral stent into theurinary system; (f) inserting the catheter into the urinary system; and(g) removing the catheter from the urinary system subsequent topositioning the ureteral stent.
 18. A ureteral stent, comprising: (a) anelongated portion defining a lumen and having a length sufficient toextend substantially within the ureter from a kidney of a user to abladder of the user; (b) a first end portion extending from one end ofthe elongated portion, the first end portion having a lumen incommunication with the lumen of the elongated portion, the first endportion having at least one opening in communication with the lumen ofthe first end portion, the first end portion for placement substantiallywithin the kidney and adapted to assume a retaining configuration whenplaced substantially within the kidney; and (c) a second end portionextending from another end of the elongated portion and flaring outwardwhen placed substantially within the bladder to maintain positionsubstantially within the bladder, the second end portion beingcollapsible after implantation to at least partially prevent fluid frompassing into the lumen, the second end portion having a plurality ofseparate segments.
 19. The stent of claim 18, wherein the second endportion comprises a plurality of inner segments and a plurality of outersegments, each one of the plurality of outer segments overlapping atleast one of the plurality of inner segments.
 20. The stent of claim 19,wherein the plurality of inner and outer segments comprise a polymer.21. The stent of claim 19, wherein the plurality of inner and outersegments comprise a polymer solution.
 22. The stent of claim 21, whereinthe polymer solution comprises polyurethane and polycarbonate.
 23. Thestent of claim 18, wherein each one of the plurality of inner and outersegments includes a plurality of folds.
 24. The stent of claim 18,wherein each of the plurality of segments being adjacent and overlappingat least one other of the plurality of segments.
 25. The stent of claim18, wherein each one of the plurality of segments includes a pluralityof folds.